Successive deuteration in low-mass star-forming regions: the case of D${}_2$-methanol (CHD${}_2$OH) in IRAS 16293-2422

Abstract

Accurate quantification of the column density of di-deuterated methanol is a key missing puzzle piece in the otherwise thoroughly constrained family of D-bearing methanol in the deeply embedded low-mass protostellar system and astrochemical template source IRAS16293-2422. A spectroscopic dataset for astrophysical purposes is built for CHD${}_2$OH and made publicly available to facilitate accurate characterization of this species in astrochemical surveys. The newly computed line list and partition function are used to search for CHD${}_2$OH towards IRAS16293-2422 A and B in data from ALMA-PILS. Only non-blended, optically thin lines of CHD${}_2$OH are used for the synthetic spectral fitting. The constructed spectroscopic database contains line frequencies and strengths for 7417 transitions in the 0 to 500 GHz frequency range. ALMA-PILS observations in the 329-363 GHz range are used to identify 105 unique, non-blended, optically thin line frequencies of CHD${}_2$OH for synthetic spectral fitting. The derived excitation temperatures and column densities yield high D/H ratios of CHD${}_2$OH in IRAS 16293-2422 A and B of 7.5$\pm$1.1% and 7.7$\pm$1.2%, respectively. Deuteration in IRAS 16293-2422 is not higher than in other low-mass star-forming regions. Di-deuterated molecules consistently have higher D/H ratios than their monodeuterated counterparts in all low-mass protostars, which may be a natural consequence of H-D substitution reactions as seen in laboratory experiments. The Solar System's natal cloud, as traced by comet 67P/Churyumov-Gerasimenko, may have had a lower initial abundance of D, been warmer than the cloud of IRAS16293-2422, or been partially reprocessed. In combination with accurate spectroscopy, a careful spectral analysis, and a consideration of the underlying assumptions, successive deuteration is a robust window on the physicochemical provenance of star-forming systems.

Accepted for publication in A&A; 24 pages, 18 figures, 3 tables; the full line list is made available as an electronic Table at the Centre de Données astronomiques de Strasbourg (CDS) with association to this A&A article

References in corpus (28)

• The ALMA Protostellar Interferometric Line Survey (PILS): First results from an unbiased submillimeter wavelength line survey of the Class 0 protostellar binary IRAS 16293-2422 with ALMA
• First detection of triply-deuterated methanol
• Constraining the abundances of complex organics in the inner regions of solar-type protostars
• Multilayer formation and evaporation of deuterated ices in prestellar and protostellar cores
• Chemical modelling of complex organic molecules with peptide-like bonds in star-forming regions
• Complex organics in IRAS 4A revisited with ALMA and PdBI: Striking contrast between two neighbouring protostellar cores
• Hot Corinos Chemical Diversity: Myth or Reality?
• Warm water deuterium fractionation in IRAS 16293-2422 - The high-resolution ALMA and SMA view
• The VLA Nascent Disk And Multiplicity (VANDAM) Survey of Perseus Protostars. Resolving the Sub-Arcsecond Binary System in NGC 1333 IRAS2A
• Orbital and mass constraints of the young binary system IRAS 16293-2422 A
• The ALMA-PILS survey: First detection of nitrous acid (HONO) in the interstellar medium
• Observations of nitrogen isotope fractionation in deeply embedded protostars
• Decrease of the organic deuteration during the evolution of Sun-like protostars: the case of SVS13-A
• History of the solar-type protostar IRAS16293-2422 as told by the cyanopolyynes
• High D${}_2$O/HDO ratio in the inner regions of the low-mass protostar NGC1333 IRAS2A
• Deuterium Fractionation: the Ariadne's Thread from the Pre-collapse Phase to Meteorites and Comets today
• Implications of a hot atmosphere/corino from ALMA observations towards NGC1333 IRAS 4A1
• ALMA observations of water deuteration: A physical diagnostic of the formation of protostars
• The ALMA-PILS survey: Gas dynamics in IRAS 16293$-$2422 and the connection between its two protostars
• The young protostellar disk in IRAS16293-2422 B is hot and shows signatures of gravitational instability
• The ALMA-PILS survey: propyne (CH${}_3$CCH) in IRAS 16293$-$2422
• Externally heated protostellar cores in the Ophiuchus star-forming region
• The SVS13-A Class I chemical complexity as revealed by S-bearing species. SOLIS XIII
• A study of singly deuterated cyclopropenylidene c-C3HD in protostar IRAS 16293-2422
• Torsional-rotational spectrum of doubly-deuterated dimethyl ether (CH${}_3$OCHD${}_2$) -- First ALMA detection in the interstellar medium
• The evolutionary status of dense cores in the NGC 1333 IRAS 4 region
• Deuterium fractionation of nitrogen hydrides: detections of NHD and ND${}_2$
• Gas vs. solid phase deuterated chemistry: HDCO and D${}_2$CO in massive star-forming regions

Cited by in corpus (7)

• Methanol deuteration in high-mass protostars
• Complex organic molecules detected in twelve high-mass star-forming regions with Atacama Large Millimeter/submillimeter Array (ALMA)
• Millimetre and sub-millimetre spectroscopy of doubly deuterated acetaldehyde (CHD2CHO) and first detection towards IRAS 16293-2422
• ALMA ACA study of the H${}_2$S/OCS ratio in low-mass protostars
• Rotational spectroscopy of oxirane-\textit{2,2}-$d_2$, $c$-CD${}_2$CH${}_2$O, and its tentative detection toward IRAS 16293$-$2422~B
• Investigation of the rotational spectrum of CD${}_3$OD and an astronomical search toward IRAS 16293$-$2422
• Gas phase Elemental abundances in Molecular cloudS (GEMS). IX. Deuterated compounds of H2S in starless cores